Virtual Image & domes - some questions

For those that know me, they know that i am not so good on technical thinks..

In general the only that i know about this subject is that a dome underwater create a virtual image and that the lens that u use must focus on this virtual Image or it kan't focus att all.

I use a old Athena OPD 170 dome to my Nexus D200 housing

Those domes are not more in production but they are exelent in Glas quality and so on.

Athena buid same domes now for the Sea & sea housings .. can I use those recommentations that athena have for the sea & sea housings?

The dome works great with my Nikon 10,5mm and Tokina 12-24

but i love to use it with some lenses as Nikkon 24/2,8Ｄ and Sigma 15mm

Is there any formula or way to see if the dome will work with those lenses before i buy and test them?

I know that may I sound silly but i have not the posabillity to find or rent a lens for testing.

Then one more question.. If the lens is focus corectly that means that i dont need diopters or can it be that with a diopter the image quality may be better?

Hi Lambis, check this page:

http://wetpixel.com/i.php/full/dome-theory/

The recommendations depend not only on dome size and curvature but also on how far the camera is from the dome. The problem is that the relative position of the camera inside the housing varies according to manufacturer.

Now, in the Subal, I use the same port with the 10.5 and the 16 fisheye, so I think that your port would also work with the sigma 15, but I'm not sure. A solution would be renting these lenses and trying them in a pool, or maybe borrowing them from a fellow photographer. But I don't know how useful they would be since their focal lengths are also covered by the 12-24.

Luiz

Luiz reason that i like to do that is that i ma not happy with the

Tokina 12-24

To much chromatic aberation and only f4 for my way off taking photos..

Now my port is this but its look lite stramge if they will work with all those lensesAthena opd 170

Lambis, my gut feeling is that the 15mm Sigma and the 24mm should be perfect with the dome, I use (used) the 24mm and the 16mm fisheye behind an Aquatica dome without changing anything, so it should go sans problem. <_<

Oh thanks Jean

I think to that it will work will try the 24 next week and the 16mm works great as you say. have test it with good results..

Great to have just one dome and so many lenses

Hi Lambis

Just wondering what ext ring you are using with the 12-24mm - are the edges soft or sharp?

Hi Col

I use a 30cm extension with my Tokina 12-24

Now about soft or sharp edges . I really havent test is as I shoot all the time people in pools

But here 2 photos ... (I think its F4 - F5) you telp me... are they sharp?

I dont know eather if i need a diopter ...